System And Methodology For Supplying Diluent

ABSTRACT

A technique facilitates various well operations by delivering a diluent to a desired location in a borehole. A completion system may be disposed in the borehole and a diluent flow path is routed along an interior of the completion system to a desired location. In some applications, the diluent is delivered to an artificial lift system, e.g. an electric submersible pumping system, to dilute a fluid being produced. A flow control unit is positioned along the diluent flow path and may be selectively actuated to control flow of the diluent to the desired location.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present document is based on and claims priority to U.S. Provisional Application Ser. No. 61/901762 filed Nov. 8, 2013, which is incorporated herein by reference in its entirety.

BACKGROUND

Hydrocarbon fluids such as oil and natural gas are obtained from a subterranean geologic formation, referred to as a reservoir, by drilling a well that penetrates the hydrocarbon-bearing formation. Once a wellbore is drilled, various forms of casing and other well completions may be deployed downhole. Sometimes, completion systems employ or work in cooperation with an electric submersible pumping system which may be used to pump oil or other hydrocarbon fluids to a collection location. In some environments, the fluids may be of relatively high viscosity and can thus inhibit pumping of the fluid via the electric submersible pumping system.

SUMMARY

In general, a system and methodology are provided for facilitating various well operations by delivering a diluent to a desired location in a borehole. For example, a completion system may be disposed in the borehole and a diluent flow path is routed along an interior of the completion system to a desired location. In some applications, the diluent is delivered to an artificial lift system, e.g. an electric submersible pumping system, to dilute a fluid being produced. A flow control unit is positioned along the diluent flow path and may be selectively actuated to control flow of the diluent to the desired location.

However, many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain embodiments of the disclosure will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. It should be understood, however, that the accompanying figures illustrate the various implementations described herein and are not meant to limit the scope of various technologies described herein, and:

FIG. 1 is a schematic illustration of an example of a well system deployed in a borehole, according to an embodiment of the disclosure;

FIG. 2 is a cross-sectional illustration of an example of a flow control unit which may be used in a well system of the type illustrated in FIG. 1, according to an embodiment of the disclosure;

FIG. 3 is a cross-sectional illustration similar to that of FIG. 2 but showing the flow control unit in a different operational position, according to an embodiment of the disclosure;

FIG. 4 is a cross-sectional illustration of another example of a flow control unit which may be used in a well system of the type illustrated in FIG. 1, according to an embodiment of the disclosure;

FIG. 5 is a cross-sectional illustration similar to that of FIG. 4 but showing the flow control unit in a different operational position, according to an embodiment of the disclosure;

FIG. 6 is a cross-sectional illustration of another example of a flow control unit which may be used in a well system of the type illustrated in FIG. 1, according to an embodiment of the disclosure;

FIG. 7 is a cross-sectional illustration similar to that of FIG. 6 but showing the flow control unit in a different operational position, according to an embodiment of the disclosure;

FIG. 8 is a cross-sectional illustration of another example of a flow control unit which may be used in a well system of the type illustrated in FIG. 1, according to an embodiment of the disclosure; and

FIG. 9 is a cross-sectional illustration similar to that of FIG. 8 but showing the flow control unit in a different operational position, according to an embodiment of the disclosure.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to provide an understanding of some embodiments of the present disclosure. However, it will be understood by those of ordinary skill in the art that the system and/or methodology may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.

The disclosure herein generally involves a system and methodology which facilitate various well operations by delivering a diluent to a desired location in a borehole. For example, the diluent may be delivered downhole to mix with a production fluid prior to pumping the production fluid to a collection location. The diluent can help reduce the viscosity of the production fluid (or other well fluid) to facilitate pumping of the fluid to the desired collection location. However, the diluent may comprise various types of substances selected to change other characteristics of the well fluid which is then pumped or otherwise moved to the collection location.

In an embodiment, a completion system may be disposed in a borehole, e.g. a wellbore. In this example, a diluent tubing is used to create a diluent flow path routed along an interior of the completion system to a desired location. In some applications, the diluent is delivered to an artificial lift system, e.g. an electric submersible pumping system, to dilute a fluid being produced or otherwise moved to a collection location. A flow control unit is positioned along the diluent flow path and may be selectively actuated to control flow of the diluent to the desired location, e.g. a downhole mixing location. By mixing the diluent with the well fluid, the characteristics of the well fluid are changed to facilitate pumping of the well fluid and/or to facilitate other operations related to the well fluid.

Referring generally to FIG. 1, a well system 20 is illustrated as deployed in a borehole 22, e.g. a wellbore. The well system 20 comprises a diluent delivery system 24 which is positioned in the borehole 22 to deliver a diluent 26 to a desired location 28. At the desired location 28, the diluent 26 is mixed with a well fluid 30 so as to adjust the characteristics of the well fluid 30. By way of example, the diluent 26 may be used to lower the viscosity of the well fluid 30 to facilitate transfer of the well fluid to a desired collection location, e.g. a surface collection location. In the embodiment illustrated, the well system 20 further comprises an artificial lift system 32 which intakes both the diluent 26 and the well fluid 30 so as to transfer, e.g. produce, a mixture 34 of the well fluid 30 and diluent 26 to the collection location.

In the specific example illustrated, well system 20 may comprise a wellbore casing 36 having, for example, a primary casing 38 and a liner 40 suspended from the primary casing 38. In this example, a lower completion 42 is run downhole into the borehole 22 and suspended within liner 40. In some applications, the lower completion 42 may be run downhole via a surface rig.

Depending on the specific well application, the lower completion 42 and the overall well system 20 may comprise a wide variety of components and systems. By way of example, lower completion 42 may comprise a sand control packer 44, a sand screen or a plurality of sand screens 46, and zonal isolation packers 48. In production applications, well fluid, e.g. oil, flows from a surrounding formation 50 and into the lower completion 42 through sand screens 46.

In the example illustrated, an upper completion 52 is engaged with lower completion 42. The upper completion 52 may be run downhole simultaneously with lower completion 42; or the upper completion 52 may be run downhole in a subsequent operation for engagement with the pre-positioned lower completion 42. The upper completion 52 also may comprise a variety of components and systems depending on the parameters of a given well operation. By way of example, the upper completion 52 may comprise a tubing 54, e.g. production tubing through which the well fluid entering via sand screens 46 may be produced to a surface location or other suitable location. Additionally, the upper completion 52 may comprise a variety of valves, such as inflow control valves 56, chemical injection valves 58, ball valves 60, safety valves 62, an/or other types of valves. Examples of other components of upper completion 52 comprise a production packer 64 which may be sealed against casing 36, e.g. against an internal surface of liner 40. The upper completion 52 also may comprise a seal assembly and/or sand control packer 66. However, various other and/or additional components and systems may be used by one or both of the lower completion 42 and upper completion 52.

In the embodiment of FIG. 1, the artificial lift system 32 is deployed down into the upper completion 52, e.g. into the tubing 54. As illustrated, the artificial lift system 32 may comprise an electric submersible pumping system 68 having an intake 70 for receiving both the well fluid 30 and the diluent 26 at location 28. The electric submersible pumping system 68 may comprise a variety of components, such as a submersible pump 72, a motor 74 for powering the submersible pump 72, a motor protector or seal section 76, and a discharge 78. During operation of pumping system 68, the mixture 34 of well fluid 30 and diluent 26 is discharged through the discharge 78 and into an interior 80 of tubing 54 above a packer 82. The packer 82 forms a seal between the electric submersible pumping system 68 and the surrounding tubing 54. A power cable 83 may be routed from the surface and used to supply electrical power to motor 74.

The diluent delivery system 24 also may comprise a variety of components and configurations. In the example illustrated, the diluent delivery system 24 comprises a diluent tubing 84 which establishes a diluent flow path appropriately routed to deliver diluent 26 to the artificial lift system 32, e.g. to the electric submersible pumping system 68. The diluent flow path is separate from the well fluid flow path along which the mixture 34 of well fluid 30 and diluent 26 travels to the desired collection location. By way of example, the diluent tubing 84 may be disposed within tubing 54 such that the diluent tubing 84 extends to a surface location along the interior of tubing 54. In some applications, the diluent tubing 84 may be in the form of a conveyance coupled to the artificial lift system 32, thus allowing the diluent tubing 84 to be used for delivering the artificial lift system 32 downhole to the desired location within tubing 54. In the illustrated example, the diluent flow path also is routed along a packer pass through 86 which allows the diluent to flow through the packer 82 to the desired location 28.

The diluent delivery system 24 further comprises a flow control unit 88 positioned along the diluent flow path, e.g. along diluent tubing 84. The flow control unit 88 is operable to control the flow of diluent 26. For example, the flow control unit 88 may be actuated to selectively allow or prevent flow of diluent 26 along the diluent flow path. In some applications, the flow control unit 88 may be selectively actuated via application of a sufficient pressure differential to the flow control unit 88.

Referring generally to FIGS. 2 and 3, an embodiment of the flow control unit 88 is illustrated. Flow control unit 88 is mounted along the flow path for diluent 26 and, in the illustrated embodiment, the flow control unit 88 is mounted along diluent tubing 84. By way of example, the flow control unit 88 may comprise a mounting structure 90 which engages sections of the diluent tubing 84 via a suitable fastening mechanism 92, e.g. threaded regions or other suitable fastening mechanisms. The mounting structure 90 further comprises a flow port or flow ports 94. Additionally, a spring-loaded seal element 96, such as a cup packer, may be coupled with or positioned in cooperation with mounting structure 90. The spring-loaded seal element 96 comprises a resilient sealing portion 98 and a spring portion 100 which biases the sealing portion 98 toward an inside surface of diluent tubing 84.

The spring-loaded seal element/cup packer 96 is oriented to block flow in the direction of arrows 102 when, for example, the pumping of diluent 26 from a surface location is stopped (see FIG. 2). However, when a sufficient differential pressure is established across the flow control unit 88 the resilient sealing portion 98 is flexed to an open flow position so that diluent 26 may flow through ports 94 and past the spring-loaded seal element 96, as illustrated in FIG. 3 and as represented by arrows 104. The pressure differential may be established by increasing the pressure of diluent 26 in diluent tubing 84 above flow control unit 88 via, for example, a surface diluent pumping system.

Once the pressure (P1) is sufficiently greater than the pressure (P2), the spring-loaded seal element 96 is forced to the open flow position. The spring-loaded seal element 96 may be constructed to transition to the open flow position upon exposure to a sufficient pressure differential (P1-P2). In other words, when the pressure differential (P1-P2) is greater than a predetermined set point, the flow control unit 88 is actuated to an open flow position to allow flow of diluent 26 to the desired location 28. The set point may vary depending on the parameters of a given application. In some embodiments, the set point may be in the range of 250-1000 psi or in a narrower range such as 450-550 psi. However, other applications may utilize other pressure differentials/set points for actuation of the flow control unit 88 between operational positions.

Referring generally to FIGS. 4 and 5, another embodiment of the flow control unit 88 is illustrated. This embodiment is similar to the embodiment illustrated in FIGS. 2 and 3, but an inflatable packer 106 is used in place of the spring-loaded seal element 96. The inflatable packer 106 comprises a sealing element 108 which may be expanded to sealingly engage the diluent tubing 84 along an interior of the diluent tubing. The sealing element 108 may be coupled with a pair of base members 110 which are mounted on mounting structure 90 and sealed thereto via a plurality of seals 112. One of the base members 110 may be fixed while the other base member 110 may be floating to enable transition between closed and open flow positions, as illustrated in FIG. 4 and FIG. 5, respectively.

In this embodiment, mounting structure 90 comprises an internal cavity 114 which contains a pressurized fluid 116 used to inflate sealing element 108 through a port 117. The internal cavity 114 may be closed to contain the pressurized fluid 116, or the pressurized fluid 116 may be supplied via a suitable control line or other source of supply. Consequently, the actuation of flow control unit 88 is affected by pressure (P1) on one side, pressure (P3) on the opposite side, and pressure (P2) within internal cavity 114 and inside sealing element 108.

Once the pressure (P1) is sufficiently greater than the pressure (P3), the sealing element 108 is forced inwardly to the open flow position by spreading the base members 110, as illustrated in FIG. 5. The sealing element 108 may be constructed to transition to the open flow position upon exposure to a sufficient pressure differential (P1-P2). In some embodiments, the pressure (P2) within cavity 114 and within sealing element 108 is adjustable to enable adjustment of the pressure differential or set point at which the sealing element 108 transitions from the closed position (FIG. 4) to the open flow position (FIG. 5). In this latter embodiment, once the set point is selected the flow control unit 88 is selectively transitioned to the open flow position when the pressure differential (P1-P3) is greater than the predetermined set point.

Referring generally to FIGS. 6 and 7, another embodiment of the flow control unit 88 is illustrated. This embodiment is similar to the embodiment illustrated in FIGS. 4 and 5, but an inflatable balloon 118 is used in place of the inflatable packer 106. The inflatable balloon 118 comprises a sealing element 120 having a slidable end 122 which may slide along mounting structure 90 similar to the movable base member 110. The slidable end 122 is able to float which enables transition between closed and open flow positions, as illustrated in FIG. 6 and FIG. 7, respectively. In some applications, a balloon support 123 may be located at the fixed end of the sealing element 120 along mounting structure 90.

In the embodiment illustrated in FIGS. 6 and 7, the sealing element 120 comprises an internal cavity 124 which may be inflated to a desired pressure P3 so as to establish a desired pressure differential/set point at which the flow control unit 88 is transitioned between closed and open flow positions. As with the embodiment described with reference to FIGS. 1 and 2, the actuation of flow control unit 88 is affected by pressure (P1) on one side and pressure (P2) on the opposite side of the flow control unit 88.

Once the pressure (P1) is sufficiently greater than the pressure (P2), the sealing element 120 is forced inwardly to the open flow position by shifting the slidable end 122, as illustrated in FIG. 7. The pressure (P3) within internal cavity 124 of sealing element 120 is selected to establish a desired pressure differential or set point at which the sealing element 120 transitions from the closed position (FIG. 6) to the open flow position (FIG. 7). The flow control unit 88 is selectively transitioned to the open flow position when the pressure differential (P1-P2) is greater than the predetermined set point.

Referring generally to FIGS. 8 and 9, another embodiment of the flow control unit 88 is illustrated. In this embodiment, flow of diluent 26 is controlled by a ball valve 126 positioned along the diluent flow path, e.g. along diluent tubing 84. The ball valve 126 may be mounted in a ball valve housing 128 and selectively actuated, e.g. pivoted, via a ball valve operator 130 slidably mounted in a chamber 132 of ball valve housing 128. The ball valve operator 130 comprises a piston 134 sealably engaging an inside surface defining chamber 132 via a suitable seal 136. A spring 138 acts against piston 134 to bias the ball valve operator 130 and thus the ball valve 126 to a closed position, as illustrated in FIG. 8. In some applications, a pressure relief valve 140 may be positioned within a ball 142 of ball valve 126.

In this embodiment, spring 138 biases ball valve operator 130 and ball valve 126 to the closed position when the artificial lift system 32, e.g. electric submersible pumping system 68, is off. When the electric submersible pumping system 68 is turned on and operated, the fluid discharged into tubing 54 via discharge 78 establishes a discharge pressure (Pd) which acts on piston 134 via a port 144 extending through the ball valve housing 128. The port 144 is positioned on a side of piston 134 opposite spring 138 so as to operate against the spring.

In the embodiment illustrated, another port 146 is located through ball valve housing 128 on an opposite side of piston 134. The port 146 is exposed to an electric submersible pumping system intake pressure (Pi) via a passageway 148, e.g. tubing, routed to an intake side of the packer 82. Thus, one side of piston 134 is exposed to a reduced intake pressure (Pi) and the other side of the piston 134 is exposed to an increased discharge pressure (Pd) when the electric submersible pumping system 68 is operated. When the pressure differential (Pd-Pi) reaches a predetermined or set level, the force exerted by spring 138 is overcome and piston 134 is shifted. The shifting of piston 134 moves ball valve operator 130 in a direction which actuates the ball valve 126 to an open flow position, as illustrated in FIG. 9. Pressure relief valve 140 may be constructed to allow flow through ball valve 126 once ball valve 126 is in an open position and after a pressure differential acting on pressure relief valve 140 rises above a predetermined or set level. Additionally, pressure relief valve 140 may be constructed as a check valve which prevents back flow through the ball valve 126.

When in the open position, the diluent 26 flows along the diluent flow path to the desired location 28. In this specific example, the diluent 26 flows down through diluent tubing 84, through ball valve 126, through packer 82 via packer pass through passages 86, and then to the desired location 28 at the intake of electric submersible pumping system 68. If the electric submersible pumping system 68 is shut off, then Pd equals Pi and spring 138 once again shuts the ball valve 126 to block flow of diluent 26.

Depending on the application, the diluent delivery system 24 may have a variety of configurations. In embodiments described herein, the diluent delivery system 24 may be operated with no control line from the surface. Embodiments of diluent delivery system 24 also prevent uncontrolled flow of diluent injection by effectively providing check valve functionality. In other words, no diluent 26 is discharged from the diluent tubing 84 when the surface system is not pumping diluent 26. However, when the surface system is pumping diluent 26 downhole to the desired location 28, the system is able to provide a back pressure which prevents sucking of the diluent 26 into the formation 50 or into the electric submersible pumping system 68 if not desired. A variety of diluent surface systems may be used to provide a desired flow rate of the diluent 26 with an appropriately limited surface supply pressure.

Similarly, the overall well system 20 may have a variety of components and configurations. For example, the lower completion 42 and the upper completion 52 may have many types of components, sizes, and/or configurations. In some applications, the lower completion and upper completion may be combined into a single completion conveyed downhole as a single unit. In other applications, additional completions may be used to perform a desired well operation. The diluent delivery system may be used in production operations and in other well servicing operations, e.g. injection operations. Additionally, artificial lift systems other than electric submersible pumping systems may be used in some applications. The type of diluent and the flow path for delivering diluent to the desired location in a given borehole also may be selected or changed according to the parameters of a given application.

Although a few embodiments of the disclosure have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims. 

What is claimed is:
 1. A system for diluting a produced fluid, comprising: an artificial lift system deployed downhole in a wellbore to pump fluid along a well fluid flow path; a diluent tubing providing a diluent flow path routed to deliver a diluent to the artificial lift system, the diluent flow path being separate from the well fluid flow path; and a flow control unit positioned along the diluent flow path to selectively allow flow of diluent upon application of a sufficient pressure differential at the flow control unit.
 2. The system as recited in claim 1, wherein the flow control unit comprises a cup packer disposed along the diluent tubing.
 3. The system as recited in claim 1, wherein the flow control unit comprises an inflatable packer disposed along the diluent tubing.
 4. The system as recited in claim 1, wherein the flow control unit comprises an inflatable balloon disposed along the diluent tubing.
 5. The system as recited in claim 1, wherein the flow control unit comprises a ball valve disposed along the diluent tubing.
 6. The system as recited in claim 1, wherein the artificial lift system comprises an electric submersible pumping system.
 7. The system as recited in claim 1, wherein the well fluid flow path is along an interior of a tubing and the diluent tubing is positioned within the interior of the tubing.
 8. The system as recited in claim 7, wherein an intake of the artificial lift system and the flow control unit are positioned on opposite sides of a packer expanded into sealing engagement with the tubing.
 9. The system as recited in claim 8, wherein the tubing is part of an upper completion engaged with a lower completion in a wellbore.
 10. A method, comprising: positioning an artificial lift system within a tubing of a completion located downhole in a wellbore; providing a diluent flow path along the completion so as to enable delivery of a diluent to an intake of the artificial lift system; and using a flow control unit positioned along the diluent flow path to selectively allow or prevent flow of the diluent to the artificial lift system.
 11. The method as recited in claim 10, further comprising operating the flow control unit by applying a pressure differential to the flow control unit.
 12. The method as recited in claim 10, wherein providing comprises providing the diluent flow path along a diluent tubing positioned within an interior of the tubing.
 13. The method as recited in claim 12, further comprising operating the artificial lift system to produce a well fluid up through the tubing along an exterior of the diluent tubing.
 14. The method as recited in claim 13, wherein positioning comprises positioning an electric submersible pumping system within the tubing.
 15. A system, comprising: a completion disposed in a borehole; a diluent tubing routed along an interior of the completion; and a flow control unit mounted along the diluent tubing to control flow of a diluent to a desired location along the completion, the flow control unit being actuated via pressure applied along the interior of the completion.
 16. The system as recited in claim 15, further comprising an electric submersible pumping system, the diluent tubing being routed to direct the diluent to an intake of the electric submersible pumping system.
 17. The system as recited in claim 15, wherein the flow control unit comprises a ball valve disposed along the diluent tubing.
 18. The system as recited in claim 15, wherein the flow control unit comprises a cup packer disposed along the diluent tubing.
 19. The system as recited in claim 15, wherein the flow control unit comprises an inflatable packer disposed along the diluent tubing.
 20. The system as recited in claim 15, wherein the flow control unit comprises an inflatable balloon disposed along the diluent tubing. 